The effects of different annealing processes and the PCBM modified layer for cathode on polymer solar cells are investigated.The performance of the polymer solar cells treated with post-annealing process is effectively improved compared with those treated with pre-annealing process.The open circuit voltage(Voc) and energy conversion efficiency (η) of post-annealing polymer solar cells are improved from 0.36 V and 0.85% to 0.60 V and 1.93%,respectively.The short-circuit current density(Jsc) and f...